Mttvannest

Hello all,
I'm finishing up the building of a slow poke made to look like a p-51b. The "Slow Crow". I put retracts in the wing and they opperate great. I have noticed on many other planes that the wheels wells are carved out of foam or framed in with vertical grain sheeting. Is this a must? My wheels retract into the first bay on each side of the fuse. the bay is closed off by a rib on each side and a shear web on the main spar. Is this enough? This is my first plane with retracts.

MinnFlyer

My Feedback: (4)

If you don't want to go through the extra work of lining the wheel well, that is enough, but you'll want to fuel proof the area.

Mttvannest

Minn,
Thanks for your quick reply. I was thinking about using great stuff expanding foam in the bay but i was afraid it would blow out the sheeting.

Jburry

If you want to foam it in, I'd suggest precut pieces of styrofoam or balsa, and then just trim'em up and paint it when you're done. The spray foam stuff is dangerous, as you noted. Expands for days sometimes....

khodges

My Feedback: (1)

1/64" hobby ply is great stuff to use. No more than you'll need, it won't weigh hardly anything, is very flexible, you can cut it with scissors like paper, and is stronger than you would think. Make templates from stiff paper, (trial and error) and then trace to the ply, cut it out, Ca in place.

mscic-RCU

My Feedback: (6)

go to the local grocery store deli and look at the deli containers. get a couple of the right size, cut them down glue them in. works great.

Mttvannest

I used light ply to sheet the bay where the wheels are. It is perfect for the job as said before.
Mscic, I'm not sure how you are using the deli tray? The bay where the wheel retracts is about 3" front to back, 5" wide, and 1/2 deep. Right now i'm just planning on leaving it hollow in that area. I was just worried that air would scoop in there and kinda of baloon the wing apart.

da Rock

The foam boxes you get lots of places are usually about 3/32" thick foam. You can cut the flat parts out and use it like sheet balsa. Sometimes the corners are the right curve for special uses. Burger King used to serve Whoppers in a box that a certain part of the bottom made a good airscoop.

As for your wing scooping air, don't worry about that, but do consider that you really only have the back of the wheelwell to deal with. I fly off of grass. No way am I going to leave the rear of the well open to catch whatever junk the tires kick up. It takes so little time to stick a piece of balsa sheet in there. With the grain in the right direction, balsa will bend to fit the curve with no effort at all. And the foam from carryout boxes works good too. I'd use the balsa however, because it's grain greatly strengthens the wing in that area. The foam does a little of that, but even 1/16" balsa adds a bunch of strength.

Mttvannest

Sounds good. Thanx so much for all the advice. I saw a quote from Dave Brown that I think applies. He said that pattern planes would show the difference if one hindge gap was 1/32nd bigger, but they never seemed to mind whacking big holes in the wing for wheels!
I would have to agree! I have seen planes with some crazy big holes stay in the air.

Matt

fredsedno

Mttvannest,
If tou use styrofoam DO NOT wipe down or clean with acetone or lacquer thinner.They will melt styrofoam.
Fredsedno

da Rock

I would like to add something.

Wings get a bunch of their spanwise strength from the spars, right. And lots of them have shear webbing between those spars to get even more strength. But lots of fully sheeted wings get their strength from the sheeting. The grain of the skin does most of the work, but having the balsa there does the trick.

So what happens when a wheelwell does away with the continuity of the skin. Right in the area around the spars and where the wing sees the most bending stress, we hack a huge hole.

I always stick some 1/16" (at least) balsa in the wheelwell for two reasons. I fly year round and an opening in a wing can collect all manner of trash. And I like to know the wing skin that no longer is there to provide strength has something in it's place.

Here is a picture of the back of the wheelwell of a P40 ARF I did back in the summer of '06. I've wiped all manner of stuff out of it. You might even notice some wear and tear in the picture.

It actually doesn't take much time to do it with scrap balsa. With the grain sticking out of the hole, the stuff bends to the radius easy. Piece of cake. Cheap waterbase polyurethane seals really good.